The developments described above put ED in an interesting position. While in classical physics it is often difficult to construct a Hamiltonian directly, without first appealing to the notion of a Lagrangian,Indeed, in [1]}[2]}, for example, C. Teitelboim sets out to determine a set of covariant dynamical theories without first appealing to a Lagrangian. His method is successful, but his method of constructing the Hamiltonian is much more tedious than if he had just began with a Lagrangian. And Dirac, who was a major proponent of the Hamiltonian viewpoint, in [3]} himself advocated beginning from a Lagrangian. in ED much of the Hamiltonian is fixed simply by requiring that it reproduce the FP equation. That is, the FP equation, which results directly from the rules of inference, fixes a good portion of the eventual quantum dynamics.
